gopls/internal/settings: document why unusedvariable is off

Updates golang/go#48975
Updates golang/go#54373

Change-Id: I6537ee08ae87e75ce47fdac63f6286048ec666e9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/640040
Reviewed-by: Robert Findley <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: adonovan

gopls/internal/settings/analysis.go

@@ -197,13 +197,7 @@ func init() {
 		{analyzer: fillreturns.Analyzer},
 		{analyzer: nonewvars.Analyzer},
 		{analyzer: noresultvalues.Analyzer},
-		// TODO(rfindley): why isn't the 'unusedvariable' analyzer enabled, if it
-		// is only enhancing type errors with suggested fixes?
-		//
-		// In particular, enabling this analyzer could cause unused variables to be
-		// greyed out, (due to the 'deletions only' fix). That seems like a nice UI
-		// feature.
-		{analyzer: unusedvariable.Analyzer, nonDefault: true},
+		{analyzer: unusedvariable.Analyzer, nonDefault: true}, // not fully baked; see #54373
 	}
 	for _, analyzer := range analyzers {
 		DefaultAnalyzers[analyzer.analyzer.Name] = analyzer